Absorbent article

ABSTRACT

The invention relates to an absorbent article, such as a sanitary towel, diaper or bandage, having an upper layer or topsheet made of a liquid-impermeable material, the topsheet being provided with openings and being intended to lie against the body of the wearer. The invention is mainly characterized in that the openings are located in depressions arranged in the topsheet and in such wall portions of the depressions which, when seen from the mouths of the depressions, form at least a right angle to the plane of the topsheet; and in that the bottoms of the depressions, when projected perpendicularly to the plane of the topsheet, substantially cover the mouths of the depressions in this plane.

The present invention relates to an absorbent article, such as asanitary towel, a diaper or bandage, of the kind which comprises aliquid-impermeable upper layer or topsheet which is provided withapertures over at least a part of its area and which is intended to lieagainst the body of the wearer, and which further comprises an absorbentbody located beneath said topsheet.

With absorbent articles of this nature it is of particular importancethat the topsheet facing the wearer is dry, even when the article hasbeen worn for an extended period of time.

One serious disadvantage with the majority of such absorbent articleshitherto known to the art is that they are liable to cause chafing ofthe skin after having been in contact with liquid, such as urine, overlong periods of time.

Hitherto, a general solution to this problem has been to use a topsheetor upper layer made from a hydrophobic material, so as to draw moisturefrom the skin into the absorbent body by suction. It has been found withsuch absorbents, however, that when the absorbent body is pressedagainst the wearer, moisture which has earlier been taken up into theabsorbent body will penetrate the thin hydrophobic layer and wet theskin of the wearer.

It is true that good insulation between the wearer's skin and anabsorbent body can be achieved with a relatively thick, loosely boundfibre-layer. This layer does not conduct liquid, but merely allows it topass straight through and thus the liquid "falls" right through thefibre-layer and into the absorbent body lying thereagainst. Suchinsulating layers, however, present problems in manufacture. One suchmanufacturing problem is that of of bonding the fibre-layer to thetopsheet.

In an attempt to provide satisfactory liquid-insulation between the skinof the wearer and the absorbent body, there has been used a topsheetcomprising a hydrophobic non-woven material which is embossed so as toincrease the volume thereof. One such liquid-insulating absorbentproduct is described in U.S. Pat. No. 4,041,951. The non-woven layercomprises a large number of downwardly projecting bead-like formationswhich rest against the planar surface of the absorbent body, while thoseareas of the non-woven layer which are not depressed when the article isin use, lie against the skin of the wearer. The intention in thisrespect is to impart to the topsheet sufficient strength to hold the wetabsorbent body away from the skin of the user, even when the absorbentarticle is subjected to high compressive forces during use. One seriousdrawback with such topsheets is that they are much too stiff anduncomfortable.

The U.S. Pat. No. 3,814,101 describes an absorbent article in which thetopsheet comprises a sheet of liquid-impermeable plastics materialhaving a plurality of slits formed therein. The topsheet also has formedtherein a large number of depressions or craters. As these depressionsare formed, the material located therein, and also the material locatedtherearound, is stretched, so as to widen the slits and permit liquid topass therethrough. The concept behind this design is that when theabsorbent body becomes saturated with body fluid, it will swell and inso doing force the depressions back to a position in which the slits areclosed. One drawback with a product of this design, however, is that thenumber of slits required to provide for satisfactory throughflow ofliquid is so numerous that the topsheet is rendered extremely brittleand sensitive to wear. One reason for using a plastics sheet instead ofa fibre-layer is to obtain a stronger topsheet. This is obviously notachieved with a slitted plastics sheet. Another inherent disadvantagewith an absorbent body produced in accordance with this latter patent isthat there is a grave risk of body fluids being unable to pass throughthe slots and into the absorbent body, and leaking through the sidesinstead.

U.S. Pat. No. 3,929,135 describes a plastics sheet provided with conicalcapillaries, which permit liquid to be transferred freely from the userinto the absorbent body while preventing flow in the opposite directionat the same time. Because such a topsheet provides a surface which whenin contact with the skin of the user is much drier than those topsheetspreviously used, such a topsheet can be said to constitute abreakthrough in the use of topsheets for absorbent products of the kindin question. The narrower part of respective conical capillaries facesthe absorbent body, which results in liquid present in the outer surfaceof the topsheet being rapidly drawn into the absorbent body by suction,while effectively preventing liquid transfer in the opposite directionat the same time.

The use of such a plastics sheet as the topsheet of an absorbentarticle, however, requires the total specific area of the throughflowopenings (apertures) to be significantly large, so as to obtain asatisfactory throughflow of liquid. As a result of the large number ofapertures required, the topsheet becomes transparent and has, interalia, the negative effect of imparting to the topsheet the appearance ofbeing wet, even though it is dry.

This drawback is particularly manifest when the transparent topsheetwhich is to face the skin of the wearer forms part of a sanitary towelor a bandage.

Although the topsheet provided with conical capillaries in accordancewith U.S. Pat. No. 3,929,135 is superior to all known topsheets withrespect to re-wetting of the skin, the topsheet is nevertheless unableto stop re-wetting occurring as a result of the powerful compressionforces to which the absorbent article provided therewith is unavoidablysubjected during use.

An object of the present invention is therefore to provide a plasticssheet having throughflow openings arranged therein and intended forabsorbent articles of the aforesaid kind, which plastic sheet when usedas the topsheet or upper layer on said articles provides, in addition toa dry surface against the skin of the wearer, better protection againstre-wetting, and which is opaque. To this end the absorbent articleaccording to the invention is characterized in that the apertures arelocated in respective depressions arranged in the upper layer ortopsheet and in such wall portions of said depressions which, when seenfrom the respective mouths thereof, form at least a right-angle to theplane of the topsheet; and in that the bottoms of said depressions whenprojected at right angles to said plane substantially cover said mouthsof said depressions in said plane.

The invention will now be described in more detail with reference to theaccompanying drawings, which illustrate examples of various suitableembodiments of absorbent articles constructed in accordance with theinvention. In the drawings,

FIG. 1 is a plan view of a sanitary towel provided with a topsheet orupper layer according to the invention;

FIG. 2 is a sectioned view of the towel illustrated in FIG. 1, taken onthe line II--II in said Figure;

FIG. 3 is a detail view in larger scale, showing the design of theapertures which permit liquid to flow through the topsheet of the towel;and

FIGS. 4-9 illustrate further embodiments of throughflow apertures in thetopsheet of an absorbent article constructed in accordance with theinvention.

In the sanitary towel illustrated in FIG. 1, only a central region 2 ofa topsheet or upper layer 3 of the towel has been provided withapertures for the throughflow of menstrual fluid, said topsheet beingintended to face the body of the wearer when the towel is worn. Thetopsheet 3 is made of plastics film and is joined to aliquid-impermeable plastics-film bottom layer or bottom sheet 4 alongthe two ends 5,6 of the towel and along the side edges 7,8 thereof, asshown more clearly in FIG. 2. The two outer layers 3,4 enclosetherebetween an absorbent body 9, which suitably comprises mechanical orchemical fluff-pulp.

FIG. 3 illustrates the appearance of the upper layer or topsheet 3.Arranged within the central region 2 of this topsheet are depressions orcraters 10 of rightangle parallelepipedic configuration. Thesedepressions are defined by a liquid-impermeable bottom 11, two mutuallyopposing liquid-impermeable sides 12,13 and two mutually opposing opensides 14,15, these latter openings being operative as liquid throughflowopenings. As seen in FIG. 3, the topsheet also exhibits smooth, planarareas 16 between the depressions, these areas forming the surface whichwhen the article is used lies against the body of the wearer. Since theapertures or openings are formed in respective walls 14,15 of thedepressions and since said walls extend perpendicularly to the actualsurface plane of the topsheet, said topsheet will be opaque, provided ofcourse that the material from which the topsheet is made is in itselfopaque. One important advantage afforded hereby is that the bottoms ofthe depressions 10 cover the whole of the respective mouths in the planeof the topsheet formed by the intersection of respective depressionswith said plane, thereby to completely close said mouths and therebypreventing reverse flow of liquid from the absorption body in a mannerto re-wet the skin of the wearer practically completely, even when theabsorbent body is subjected to high compressive forces by the body ofthe wearer.

Another important advantage, afforded by the location of the liquidthroughflow openings in planes which are perpendicular to the surfaceplane lying against the skin of the user, is that air can flow inbeneath the depressions in a manner to reach the skin over a relativelylarge area of the surface lying directly against the skin of the wearer.As a result hereof, the topsheet forming part of an absorbent articlemade in accordance with the invention and facing the skin of the usercan never be experienced as having the nature of a plastics material.

The width of the depressions 10 in the plane of the topsheet 3 issuitably of the order of 0.1-6.0 mm. The width of said depressions isselected in accordance with the body fluid to be absorbed by theproduct. Although FIGS. 1-3 illustrate embodiments of a sanitary towelconstructed in accordance with the invention, it will be understood thatthe surface material formed in accordance with the invention can also beused with diapers and bandages. The choice of the size of thedepressions and the distance at which they are spaced apart iscontingent upon the droplet size of the body fluid to be absorbed. Inthis respect, the interspace between adjacent depressions should not beof such magnitude that droplets can remain lying on the smooth area 16located between adjacent depressions 10.

The size of the openings 14,15 in the walls of the depressions issuitably in the range of 0.05-2.5 mm. More specifically, the choice ofopening-size is made with respect to the width of the depressions in theplane of the topsheet 3 so that liquid droplets reaching the depressions10 are drawn by suction into the absorbent body 9, through the openings14,15 located in the depression walls.

FIG. 4 illustrates an alternative embodiment of the depressionsillustrated in FIG. 3. The depressions of the FIG. 4 embodiment arecylindrical and have a circular bottom 16. Located in the cylindricalwalls are three relatively large holes 17, and of the actual walls ofeach depression there remains only three strips 18. The check-valveeffect of this embodiment has been found particularly effective. Thewall strips 18 will give way even when the pressure between theabsorbent body and the user is relatively light, thereby to close themouths of the depressions in the plane of the topsheet 3, with the aidof the bottoms 16, these bottoms readily returning to the originalpositions immediately the liquid pressure acting from the upper side ofthe absorbent article exceeds the pressure acting from the absorbentbody.

If more rigid cylindrical depressions having a less noticablecheck-valve effect are desired, the cylindrical walls 20 of thedepressions may be provided with a single opening 19, in accordance withthe embodiment illustrated in FIG. 5. In this embodiment, the size of arespective bottom 21 coincides with the mouth of a respective depressionin the plane of the topsheet or upper layer 3.

In the embodiment illustrated in FIG. 6, respective depressions are oftriangular cross-sectional shape and comprise two walls 23, 24, athrough-flow opening 25 and a bottom 22.

The embodiment of the depressions illustrated in FIG. 7 differs from thepreviously described embodiments, insomuch as the bottoms 26 of thedepressions of this embodiment slope from the upper edge 27 in the planeof the topsheet or upper layer 3 down to the lower edge of a verticalwall opening 28. The depression is given in this way two vertical,triangular walls 29. This embodiment exhibits good check-valve effects.

The embodiment illustrated in FIG. 7 can be modified to obtain theembodiment illustrated in FIG. 8, in which latter embodiment thecheck-valve effect is more pronounced.

In the FIG. 8 embodiment, the vertical opening 30 has the form of acircle segment and the depth of the depression decreases continuously,from the lower edge of the opening towards the opposite end of thedepression. In this way, when seen in a plane parallel with the opening30, the depression has the form of a circle segment. Since the bottom 31is curved and there are no vertical walls, the check-valve effectproduced with this embodiment is particularly pronounced, asbeforementioned.

In the embodiment illustrated in FIG. 9, the depression is rectangularin the plane of the topsheet or upper layer 3, and has two mutuallyopposing, vertical circle-segment shaped wall openings 32,33. The shapeof the bottom 34 over the whole of its width coincides with thecurvatures of the openings.

As beforementioned when referring to the embodiment illustrated in FIGS.1-3, the openings in the side walls of the depressions are smaller thanthe mouths of the depressions in the plane of the topsheet or upperlayer 3, thereby to produce a suction effect, by means of which liquidreaching the depressions is drawn into the absorbent body. This suctioneffect can be further amplified, by applying a thin layer of fibres tothe inner surface of the topsheet. These fibres will cross the verticalwall openings of the depressions in a manner to decrease the effectivesize of said openings, with an increased suction effect as a resultthereof.

The aforedescribed plastic topsheet or upper layer provided withdepressions and through-passing openings is suitably manufactured byvacuum-forming against a matrix having the desired configuration of thearticle. In this respect, the openings can be formed, for example, bymeans of cutting surfaces located on the matrix, or with the aid of aflowing medium directed against the topsheet and matrix.

The invention is not restricted to the aforedescribed embodiments, sincea number of modifications can be made within the scope of the followingclaims.

For example, the walls of respective depressions can be strengthened towithstand large compression forces, i.e. to counter-act the check-valveeffect. In this respect, the walls may be strengthened by corrugatingsaid walls or by coating them with reinforcing fibres.

As will be understood, the openings in the depression walls need notextend over the entire height of the respective walls. Instead, theopenings may be made to terminate at a distance from the plane of thetopsheet or upper layer 3.

In certain conceivable embodiments of the depressions the depressionsmay lack a true bottom, for example in such depression configurations inwhich the depression is tubular and in which the longitudinal axisthereof forms an angle other than 90° with the plane of the topsheet andsaid depressions are open at respective ends. Thus, the term "bottom"used in the following main claim may comprise, either totally orpartially, wall portions of the depressions. It will be understood fromthis that the "bottom" of a depression comprises those wall portionsand/or true bottom portions which when projected perpendicularly to theplane of the topsheet or upper layer cover the mouth of respectivedepression in said plane.

We claim:
 1. An absorbent article, such as a sanitary towel, a diaper orbandage, comprising a liquid-impermeable topsheet which is provided withopenings over at least part of its area and which is intended to lieagainst the body of the wearer, and an absorbent body located beneathsaid topsheet, the openings being arranged in depressions in thetopsheet and in such wall portions of said depressions which, when seenfrom the mouth of the depressions, form at least a right angle to theplane of said topsheet; the bottoms of said depressions, when projectedperpendicularly onto the plane of the topsheet, substantially coveringthe mouths of the depressions in said plane.
 2. An article according toclaim 1, in which the depression walls extending from the plane of thetopsheet to the bottoms of said depressions are so thin and/or have suchsmall width in relation to the opening or openings in said walls thatthe depressions operate as check valves when the absorbent body iscompressed as a result of compression forces occurring during the use ofsaid article.
 3. An article according to claim 1 in which the width ofthe depressions in the plane of the topsheet is in the order of 0.1-6.0mm; and in that the openings in the walls of said depressions have aheight in the order of 0.05-2.5 mm.
 4. An article according to claim 1,in which together the depressions constitute between 10 and 70% of thearea of the topsheet.
 5. An article according to claim 1, in which thedepressions have, overall, mutually the same depths; and in that thedepression wall or walls is, or are, substantially vertical.
 6. Anarticle according to claim 1, in which that each of the depressions hasa bottom which extends obliquely upwards, from the lower edge of a wallopening to the plane of the topsheet.
 7. An article according to claim1, in which that each of the depressions has a vertical wall opening inthe form of a circle segment; and in that the depth of said depressiondecreases away from said opening, thereby to provide a recess having agood check valve effect.
 8. An article according to any one of claim 1,in which that the depressions are of substantially rectangularconfiguration in the plane of the topsheet and are provided with twomutually opposing congruent circle segment shaped wall openings and haverespective bottoms which coincide, over the whole of their length, withthe arcuate curvature of the wall openings.
 9. An article according toclaim 1, in which that a thin layer of fibres applied to the innersurface of the topsheet, said fibre layer being adapted to amplify thetransportation of liquid through the openings of the topsheet and intothe absorbent body.